The summer of 1977 was an exciting time for space exploration. Scientists prepped twin long-distance spacecrafts for a mission to explore the far reaches of the Solar System. Voyager 2 launched earlier in the summer, but Voyager 1 departed planet Earth on September 5 (coincidentally, the same date that the space shuttle Discovery would later return to Earth in 1984). The Voyager crafts took vastly different routes, but together they helped NASA flesh out a “family portrait of four giant planets, their ring systems and magnetic fields, plus forty-eight of their moons,” according to Dreams of Other Worlds: The Amazing Story of Unmanned Space Exploration by Chris Impey and Holly Henry. Here are some other quick facts about the Voyager mission gleaned from the book which is a fascinating history of unmanned space exploration:

1.) Each Voyager spacecraft weighs about 800 kilograms, about the same as a Smart Car weighs, but much less than a Mini Cooper (surprising how much they weigh — check it out.)

3.) Attached to the body of each spacecraft is a gold-plate, copper phonograph record that contains musical selections, images, and audio greetings in many world languages. What is on this record? According to Smithsonian Magazine, this time capsule disc contains over 150 recordings including Chuck Berry’s “Johnny B. Goode”, whale songs, and a greeting from Nick Saga, Carl Sagan’s son in which he says, “Hello from the children of planet Earth.”

4.) The Voyager craft get great mileage — 80,000 miles per gallon — in part because they also use Radioisotopic Themoelectric Generators as a continuous source of power.

5.) The Voyager spacecrafts have about 160,000 Twitter followers and spend their time congratulating other Space missions. They actually have a good sense of humor as evidenced by this tweet:

6.) While the Voyager technology was cutting edge for the 1970s, it is quite obsolete now. The video camera attached to each Voyager craft was designed by RCA in the 1950s and the information they transmit travels at a rate 25,000 times slower than “basic broadband” internet service. In spite of this, Voyager supplied iconic images like this one of Neptune:

7.) Voyager 1 made lots of important discoveries about Jupiter including two new moons (Thebe and Metis) and a faint ring system. The Voyager spacecraft also observed eruptions on Io, another Jupiter moon, which marked the first time volcanic activity was observed anywhere but Earth.

In the sprint to identify planets beyond our Solar System, scientists scan the skies for habitable worlds similar to Earth with the goal of finding life beyond ours. With each new confirmation of smaller and more Earth-sized planets, and a possible 400 billion exoplanets in the Milky Way alone, the odds are high that habitable worlds abound. Several of the missions discussed in Dreams of Other Worlds by Chris Impey and Holly Henry have been instrumental in this research, including the beloved Hubble Space Telescope.

The book details the methods scientists use to detecting extrasolar planets, the wild variety of planets found so far, and the teams and researchers making the discoveries, including Planethunters.org, the online survey of Kepler data that citizen scientists are currently scouring for evidence of these worlds. The chapter on the Viking mission comments on how, in searching for life on Mars, James Lovelock and Lynn Margulis determined that volatile gases such as oxygen or ozone are replenished by living organisms in Earth’s biosphere and will be important biomarkers of life on exoplanets. The chapter on the Spitzer mission details the ways complex organisms on Earth developed eyes designed to best use the light of our own star, the Sun, as well as how life forms elsewhere might be adjusted to existence on a planet orbiting a red dwarf star, the most common star type in the Milky Way. While the Hipparcos mission inadvertently identified exoplanets orbiting other stars, its successor mission, Gaia, is poised to detect thousands more.

Beyond artist depictions of exoplanets in orbit of distant stars, the book considers the artwork of Chesley Bonestell whose imaginative paintings of planetary landscapes inspired his and future generations to consider the variable landscapes within our Solar System and beyond. And, of course, the gold-plated phonograph records attached to the ongoing Voyager spacecraft were intended for civilizations potentially inhabiting an exoplanet in our galactic neighborhood.

The book’s conclusion looks to the upcoming James Webb Space Telescope that will turn its infrared seeking lenses to the search of far-flung worlds. What we find, the authors remind us, is bound to completely rewrite our understanding of life and where it can exist, as well as our place in the unimaginably vast universe that surrounds us.

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